1. Field of the Invention
This invention relates to radar systems and particularly to an improved wide dynamic range sidelobe blanking arrangement for use in radar systems employing pulse compression.
2. Description of the Prior Art
In conventional sidelobe blanking receivers utilizing an auxiliary antenna arrangement, the sidelobe signals are processed in the sidelobe receiver in an identical manner to the processing of the signals in the main radar receiver. Energy for the sidelobe receiver is obtained from a separate antenna whose spatial coverage substantially matches that of the radar antenna sidelobe pattern. The detected outputs of the two receivers are then compared and if the amplitude of the video from the sidelobe receiver exceeds the amplitude of the radar receiver video, a blanking gate having the width of the sidelobe video is generated. This blanking gate is used for blanking the corresponding false target or any target appearing in the radar receiver at that time. However, if the amplitude of the radar receiver video exceeds that of the sidelobe receiver video, a blanking gate is not generated and the target is assumed to be real. In pulse compression systems, the comparison is made utilizing the compressed pulses, and false targets as well as very large valid targets may be removed when the signals have exceeded the dynamic range of the compression system. In pulse compression systems in which a constant false alarm rate is desired, amplitude limiting or hard limiting is utilized at points early in the system. This amplitude limiting limits the dynamic range of the compression systems and discrimination cannot be made between the two, as the two compressed signals are always of equal amplitude at the outputs of the compressors regardless of amplitude differences at the inputs. Thus, in this CFAR (constant false alarm rate) type of system, discrimination between main lobe and sidelobe returns can be made only up to the limit of the receiver's dynamic range or the compression gain above the system limit level. If blanking is employed over the uncompressed pulse width, far too much data is blanked out to be operable. It would be a substantial improvement in the art if a sidelobe blanking arrangement were provided that operated satisfactorily over the entire receiver dynamic range in a radar employing digital pulse compression and amplitude limiting for a desirable constant false alarm rate.